Assessment of the optimal plasma parameters in SPIDER for efficient negative ion production

The results of numerical studies of optimal operational conditions for efficient negative ions production in the SPIDER negative ion source are presented. Analysis are done by means of the numerical code FSFS2D which gives self-consistent two-dimensional description of the source, including neutral gas flow, plasma chemistry, RF coupling in the driver and plasma transport through the magnetic filter. Different particle species are described by separate continuity equations and the electron temperature is governed by the electron energy equation whereas the plasma potential is described by the Poisson equation. Parametric investigations have been performed assessing the influence of the negative ions production yield, magnetic filter field, gas pressure, plasma grid potential and RF heating power on the negative ions performance. It has been found that the increase of almost all the considered operational parameters leads to the enhancement of the negative ions current.